The Meprolight FRBS are tritium-enhanced, self-illuminated front and rear back-up sights designed to provide the shooter secondary sights in case the primary optics go down. FRBS sights are advanced, low-profile, durable, tritium-enhanced auxiliary front and rear back-up sights. The sights quickly fold up or down depending on the shooters needs. Sight pin elevation is easily and quickly adjusted without tools. FRBS sights are readily mounted on any 1913 Picatinny rail. Day or night, the tritium makes the FRBS a viable option. FeaturesLow profile and lightweight designCan be used as a primary or back-up sightManually adjustable, no tools neededDurable fiberglass reinforced polymer and metal constructionSpring-based locking mechanism - will not break or deformCompatible with all MIL-STD 1913 Picatinny rails